Studies have shown that men with psychogenic impotence generally have normal sleep erections, whereas men with organic impotence have sleep erections that correspond to their impaired wake performance. Such studies have alerted the scientific community of the potential usefulness of nocturnal penile tumescent monitoring in the differential diagnosis of sexual impotence. As a result of the recognition that nocturnal penile tumescent monitoring can be of assistance in diagnosing male erectile impotence, various types of devices and techniques for conducting such monitoring have been developed.
In an article entitled "A Simple and Inexpensive Transducer for Quantitative Measurement of Penile Erection During Sleep", Behavior Research Methods and Instrumentation, Volume 1, pages 251-252, 1969, Ismet Karacan describes a mercury strain-gauge tranducer for detecting penile erection. The transducer device is an elastomeric mercury filled tube which is suitably connected to a wheatstone bridge and amplifier circuit for recording purposes. As the transducer changes size during penile erection, its electrical resistance changes thereby causing the amplified output from the wheatstone bridge to change. The amplified changes in the output are recorded enabling penile activity to be recorded.
In an article entitled "Some Characteristics of Nocturnal Penile Tumescence in Young Adults", Archives General Psychiatry, Volume 26, pages 351-356, 1972, Ismet Karacan et al. describes the normative characteristics of nocturnal penile tumescence (NPT) in a group of 20 to 26 year old men who were measured during continuous all-night recording utilizing the mercury strain-gauge transducer.
Additionally, a number of devices and procedures for monitoring penile tumescence during sleep are noted and referenced in an article entitled "Sleep Related Penile Tumescence as a Function of Age", American Journal of Psychiatry, Volume 132, page 9, Sept. 1975.
In U.S. Pat. No. 4,103,678 issued to Ismet Karacan et al. an apparatus is disclosed for recording minute variations in mercury strain-gauge transducers positioned at the base and the tip of the penis.
The above-referenced materials relate to nocturnal penile tumescence activity and not to the measurement of penile rigidity or hardness during the tumescent event. While it is recognized that nocturnal penile tumescence activity is important to the evaluation of organic impotence, another significant aspect in evaluating organic impotence is the quality or rigidity/hardness achieved during the penile tumescent event.
The mercury strain-gauges described by Ismet Karacan provide a measurement of the changes in penile size during a penile tumescent event by changing their impedance as they expand and contract with variations in the penis circumference. The mercury strain-gauges do not, however, provide for measurement of penile rigidity or hardness since the strain-gauges are very elastomeric. A very slight amount of force will fully expand the strain-gauges just as would a larger amount of force.
In addition, the mercury strain-gauge necessitates a rather elaborate monitoring mechanism. The monitoring normally must occur in a health care facility under the supervision of trained experts. This requires that the patient may be in the health care facility overnight and be subjected to fairly elaborate testing. In addition to creating a substantial imposition on the patient's daily routine, substantial expense is associated with the support facilities and support personnel required to obtain valid test results.
In an article entitled "Nocturnal Penile Tumescence Monitoring with Stamps", Urology, Volume 15, pages 171-172, 1980, a stamp technique is described for detecting complete nocturnal erection for the evaluation of impotence. In this technique, a strip of four postage-type stamps is wrapped snuggly around the penis, and the overlapping stamp is moistened to provide a one half to one stamp overlapping seal. The nocturnal penile tumescent stamps, each one and one quarter by one inch, are made on ten by eight inch sheets of paper having water base glue on the opposite side. The patients or subjects are able to perform the evaluations at home rather than go to the hospital, resulting in substantial financial savings. The article indicated that three nights of inhospital nocturnal penile tumescence testing including direct observation of indicated erections and physicians professional fee, currently cost roughly $500. The stamp testing method costs 30 cents for three nights of outpatient testing.
While the stamp testing method attempts to measure penile rigidity or hardness during a penile tumescent event rather than penile activity, the stamp testing technique does not provide desired accuracy and reproducability. The stamps have a tendency to release after being wetted and stuck together. In addition, the force required to break the perforations between adjacent stamps varies substantially. Thus, the above described stamp technique does not provide a method for accurately detecting a predetermined penile rigidity or hardness.
The present invention offers a safe, simple, accurate and reproducible test which can be used at home and provides a very effective tool in the evaluation of impotence.